The present invention relates to computers and, more particularly, to computer instruction sets. A major objective of the invention is to improve computer performance when performing large numbers of table lookups.
Digital video, encryption, and code conversion are three applications in which functions of the form y=f(x) are applied repeatedly to a large number of input values. Generally, the functions applied can be expressed as mathematic expressions, but it is often more convenient to implement some functions in the form of lookup tables, with the independent variable (e.g., x) corresponding to the address and the dependent variable (e.g., y) corresponding to the contents at that address.
Lookup tables are conventionally held in main memory. A table is typically organized in memory as an array of elements, where each element holds the value of one table entry. Instructions then simply specify the desired memory locations, the contents of which are read out to provide the desired function results. While such lookups can be implemented at very high speeds, they can still limit performance in applications, such as video processing, encryption, and code conversion where very large numbers of such lookups are required. What is needed is a way to further improve performance when repeated table lookups are required.